Problem: $\dfrac{10}{10} + \dfrac{9}{100} = {?}$
Explanation: The fractions must have the same denominator before you can add them. Rewrite $\dfrac{10}{10}$ as $\dfrac{100}{100}$ $\dfrac{100}{100} + \dfrac{9}{100} = {?}$ $ = \dfrac{109}{100}$